The present invention relates to an NC (Numerical Control) system and method, and more particularly to an NC system capable of automatically changing machining conditions so as to machine a workpiece within an allowable range of the capabilities of a machine tool or a machining tool controlled by the NC system.
NC machining systems machine a workpiece by specifying the position of a tool with respect to the workpiece in the form of corresponding numerical information. The NC machining system can machine workpieces of complex configuration with ease and high accuracy at a high production rate. There has been proposed a machine tool controlled by the NC machining system, such as a lathe having a plurality of tool bases.
With prior NC machining systems, all cutting conditions have been required to be computed by the operator, and it has been quite complex to determine cutting conditions so as not to exceed the allowable range of the power and torque of the machine tool. In particular, where a lathe having a single spindle motor and a plurality of turrets or tool bases is employed to cut a workpiece with the turrets, the load imposed on the lathe is determined by the sums of powers and torques for the various cutting conditions for the respective turrets, and hence the tendency is to exceed the allowable range of the cutting tools or the machine tool.
If the allowable range of a tool such as a cutting tool or a drill bit is exceeded, the limit at which the tool cuts the workpiece is also exceeded, thus resulting in breakage of the tool. If the allowable capability range of the lathe is exceeded, the spindle motor of the lathe is subjected to an undue load, and forces are imposed tending to damage the various parts of the machine, thereby adversely affecting the machine tool. Therefore, if the sums of powers and torques exceed the allowable range of a machine tool controlled by an NC system, the operator has to change cutting conditions and compute new cutting conditions again.